1. Field of the Invention
The present invention relates to a communications apparatus for multimedia information such as an AV (Audio Visual) communications apparatus used for a television telephone apparatus, and video-conference systems.
2. Related Background Art
In recent years, along with the inauguration of the communications services through ISDN circuits, a particular attention has been given to the television telephone, video-conference systems, and other AV services which use a digital circuit of the kind.
Along the inauguration of AV services, the service regulations for AV services, protocol regulations, structural regulations of multiplexing frames for multimedia, encoding methods for animated image information, and the like are recommended as recommendations H.320, H.242, H.221, H.230, H.261 among others.
Now, with reference to the accompanying drawings, the recommendation H.221 will be described. FIG. 1 is a view which shows the frame structure regulated by the JTU-TS Recommendation H.221 for 64 kbps one channel. FIGS. 2A and 2B are views which represent the bit assignments between FAS one multiframe=eight submultiframes (one subframe=two frames).
In accordance with the Recommendation H.221, frame structures are regulated in the AV services on the 64 kbps to 1,920 kbps channels. The frame structure regulated by the Recommendation H.221 for the 64 kbps one channel is a structure constituted by 80 octet per frame. As shown in FIG. 1, numerals 1 to 8 on the axis of abscissa represent bit numbers, and numerals 1 to 80 on the axis of ordinate represent octet numbers. As shown in FIG. 1 and FIG. 2A, the FAS represents the frame synchronization signals. By these signals, the frame synchronization and multiframe synchronization are controlled. Also, the monitoring function of communications quality, the notification of warning information, and the like are controlled by the signals.
On the other hand, the BAS shown in FIG. 2B represents the bit rate assignment signals. By these signals, the terminal capability, the bit rate assignment designation per media in the actual frame, and various other controls and notifications are performed. As shown in FIGS. 2A and 2B, the BAS is transferred to the even-numbered frames, while the corresponding error correction bits are transferred to the odd-numbered frames.
The Recommendation H.242 regulates procedures such as the capability information exchanging sequence and the mode switching sequence using the inchannel BAS between AV terminals.
The Recommendation H.320 regulates the systems aspect all over the AV services.
The Recommendation H.230 regulates the transfer frame synchronization or various controls and notifications which require emergency responses as additional information regarding the functions required for the performance of AV services.
The Recommendation H.261 regulates the encoding and decoding methods for animated information at a speed of pxc3x9764 kbps (p=1 to 30).
Now, with reference to the accompanying drawings, the description will be made of the circuit which performs the videocodec function in accordance with the Recommendation H.261 conceding the encoding and decoding of animated image information. FIG. 3 is a block diagram which shows the circuit structure for performing the videocodec function according to the Recommendation H.261 conceding the encoding and decoding of animated image information.
The inputted video signals are provided with a common intermediate image format called CIF/QCIF which is regulated as a compromise plan between the NTSC and PAL methods which are the television methods of Japan, U.S.A., and European nations.
The inputted video signals are supplied to a information source encoder 201. The information source encoder 201 selects the INTRA mode, INTER mode, or MC mode per unit of macro block, executes DCT (Diffuse Cosine Transformation) of inputted image/estimated errors per block of each pixel (8xc3x978), and quantizes coefficients. Here, in the estimated processing, a two-dimensional spatial filter may be used per block of pixels (8xc3x978).
The output from the information source encoder 201 is supplied to a video signal multiplexing encoder 202. The video signal multiplexing encoder 202 performs variable encoding in accordance with the four-layered structure of a frame, a group of blocks (GOB), a macro block (MB), and a block. The output from the video signal multiplexing encoder 202 is supplied to a transmission buffer 203. The transmission buffer 203 controls encoding on the basis of the transmission rate.
The output from the transmission buffer 203 is supplied to a transmission encoder 204. The transmission encoder 204 performs transmission encoding by use of the frames for BCH (511 and 492) error correction encoding.
On the other hand, a transmission decoder 209 on the decoding side performs the operations contrary to the encoding described above by means of a reception buffer, video signal multiplexing decoder 207, and information decoder 206, thus decoding the received image signals to the CIF/QCIF video signals.
Now, with reference to the accompanying drawings, the description will be made of the fundamental sequence to execute multimedia communications on images, voices, data (all the user information other than the images and voices) and the like in accordance with the recommendations described above. FIG. 4 is a flowchart which shows the fundamental sequence regarding the execution of the multimedia communications on images, voices, data (all the user information other than the images and voices) and the like in accordance with the ITU-TS Recommendations.
At first, when a communications apparatus for multimedia information (hereinafter referred to as an apparatus on the transmission side) is actuated, the outchannel call control is actuated following this actuation so that a reception is notified to an apparatus on the reception side. If this operation is for the ISDN circuit, a call setup sequence is actuated by a Dch.
In the apparatus on the transmission side, step S1 is executed at first as shown in FIG. 4. In the step S1, whether or not the reception is a television telephone call is determined. In a case of the ISDN circuit, it is determined whether the call is a telephone call, television telephone call, or a call which differs from them completely by use of the BC (transmission capability) information element, HLC (high level layer matching capability) information element, LLC (low level layer matching capability) information element, and other information elements.
When the call is ascertained to be a television telephone call, step S2 is executed. In the step S2, the Dch call is set up to establish a first connection.
Then, step S3 is executed. In the step S3, a frame synchronization is set up by the FAS retrieval and detection, the sending out of A bit=0 and detection in the setup connection (corresponding to the Bch, Hch, or the like in the ISDN). After the synchronized setup, step S4 is executed. In the step S4, the capability of an apparatus on the reception side is determined by the capability information exchanging sequence by the capability BAS transmission and reception detections.
Then, step S5 is executed. In the step S5, a multimedia multiplexing assignment is determined in the first connection, thus executing the BAS command transmission, and the mode switching over sequence by the reception. In this way, the multimedia multiplexing communication is started. Actually, in this case, the sequences are often those executing only the voice reception when the setup of additional connections is executed continuously. For example, the communication is started in accordance with the voice 56 kbps in a mode where the H.261 image is off as shown in FIG. 4.
After the commencement of the communications, step S6 is executed. In the step S6, it is determined whether or not there is a capability of additional connection setup in its own apparatus or in the apparatus on the reception side. If affirmative, step S7 is executed. In the step S7, the additional connection is set up.
Then, step S8 is executed. In the step S8, the frame synchronization setup, multiframe synchronization setup, and a synchronism setup with the first channel are processed by utilizing the FAS retrieval of the additional connection and its detection as well as A bit.
After the completion of the synchronizing setup process, it is again determined in the step S6 whether or not there is any need for a further addition of the additional connection.
Where there is no longer any need for additional connections, step S9 is executed. In the step S9, the operational mode suitable for the utilization of all channels is determined to execute the transmission of the BAS command, and the mode switching over sequence by means of the mode switch over by the reception. For example, in FIG. 4, the H.261 image ON and voice encoding are modified to its optimal encoding between both terminals in order to execute the multimedia multiplexing communications. In this respect, it may be possible to execute the mode switching sequence by the BAS command in the Step S9 each time immediately after the synchronized setup (step S8) per additional connection.
In a television telephone apparatus and a video conference system, if an arrangement of a response message should be considered with respect to a message kept in an answer recording mode or the recording of a message from a communicating party should be made, it is possible to transmit such a response message to a voice information containing an image information or to record such information, unlike a response message to a voice information through an ordinary telephone or the recording of a message to be kept in an answer recording mode containing only voice information. In this case, however, it is impossible to determine the type of the multiplexed voice and image information on its way before actually executing the sequence of the capability information exchange with the apparatus on the transmission side. Also, since the image encoding by the application of xe2x80x9cH.261xe2x80x9d uses the estimated encoding between frames, it is not necessarily possible to keep the simply encoded voice and image information in record as a response message at all times and utilize the message by transmitting it as it is. In this respect, it is conceivably possible to provide a method in which a plurality of response messages are prepared for use by switching them over in accordance with the requirements of the communicating party, but any dynamic selection cannot be made promptly. In addition, there is a problem that the apparatus itself becomes great and inevitably expensive.
Also, even if voice information and animated image encoded information are accumulated as response messages at the same time, it is extremely difficult to transmit the fixedly synchronized voice and image information because the assignable route of image transmission is variable depending on the connected party at the time of actual circuit connection. As a result, even if the voice and image information can be transmitted, there is encountered a drawback that it is not necessarily possible to execute the decoded image representation on an apparatus on the reception side as intended by the party on the transmission side.
Particularly, whereas the voice information can be transmitted immediately, it is necessary to wait until the additional channel becomes obtainable even when a first channel has been obtained because the amount of an image information is great in transmitting a multiplexed image information. As a result, there is also encountered a drawback that the timing is delayed for starting the transmission of a response message.
On the other hand, unlike an ordinary telephone system where only a transmitted voice information is recorded, the transmitted voice and image information are multiplexed in the television telephone or video conference system when recording the message from a party on the transmission side. Therefore, the message cannot be reproduced in a good condition if the message is recorded simply as it is. There is a need for any reception of a multiplexed information to be divided into the voice and image information before being recorded.
However, even when voice information is received in a telephone mode or when voice information is received in a television telephone mode with an extremely small amount of image information contained, it is still necessary to record the information on a medium for recording image information as the medium used for recording in such a case. As a result, when the medium is for recording image information, most of it is used for recording voice information, thus resulting in the wasteful consumption of the recording medium.
Further, when the received data are encoded in frames and between frames, there is encountered a drawback that a good reproduction cannot be made because, depending on the timing of decoded recording, a recording is performed beginning with the encoded data between the frames which is a differential data with the one on the last frame.
It is an object of the present invention to provide a communications apparatus for multimedia information for which the problems described above are solved.
It is another object of the invention to provide a communications apparatus for multimedia information capable of varying response messages with respect to a communication apparatus on the reception side in accordance with the communications capability of the communications apparatus on the reception side.
It is still another object of the invention to provide a communication apparatus for multimedia information capable of executing the transmission of response messages to a communication apparatus on the reception side by different timing depending on the kinds of data.
In order to achieve the objects described above, a communications apparatus for multimedia information according to the present invention comprises means for receiving multiplexed multimedia information through a circuit; memory means for storing information containing voice information and image information as a response message to a party on the transmission side in accordance with the reception by the aforesaid receiving means; and means for transmitting the image information for use of the aforesaid response after having transmitted the voice information for use of the aforesaid response in accordance with the reception.
It is a further object of the invention to provide a communications apparatus for multimedia information which makes it possible for a communications apparatus on the communicating party""s side to identify the condition in which the messages transmitted by that apparatus are accumulated in the apparatus on this side.
It is still a further object of the invention to provide a communications apparatus for multimedia information capable of changing media for accumulating the received messages in accordance with the kinds of received messages.
It is another object of the invention to provide a communications apparatus for multimedia information capable of changing its communication capabilities at the time of indicating an answer recording communication and of executing an ordinary communication.
It is still another object of the invention to provide a communications apparatus for multimedia information which accumulates the received messages in such a way to be able to reproduce them in a good condition when these messages are reproduced.
It is a further object of the invention to provide a communications apparatus for multimedia information having new functions.
The other objects and features of the present invention will become clearer by reference to the accompanying drawings and detailed description which will be given below.